That increased tension in the jaw can impact the intrathoracic pressure (from glottis to diaphragm), which in turn, impacts the intra-abdominal pressure (from diaphragm to pelvic floor) and, you guessed it, your pelvic floor muscles! (yogauonline.com)
The top of your windpipe (your glottis) closes immediately after your diaphragm contracts which makes the typical «hic» sound.» (momtricks.com)
Their abdominal muscles are weak, and they must bear down with their diaphragm against their closed voice box (glottis). (healthline.com)